Micro led transfer method and display module manufactured by the same

ABSTRACT

A display module is provided. The display module includes: a substrate; a thin film transistor (TFT) layer formed on one surface of the substrate; and a plurality of micro LEDs disposed on the TFT layer. The plurality of micro LEDs are transferred from a transfer substrate to the TFT layer by a laser beam radiated to the transfer substrate through openings of a mask. The openings correspond to regions in which the respective micro LEDs of the transfer substrate are arranged and the openings correspond to a width, a length, or a unit area of each of the micro LEDs.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. § 119to Korean Patent Application No. 10-2019-0053285, filed on May 7, 2019,in the Korean Intellectual Property Office, the disclosure of which isincorporated by reference herein in its entirety.

BACKGROUND Field

The disclosure relates to a display module and a method of manufacturingthe display module by transferring a plurality of LEDs from a micro LEDtransfer substrate to a target substrate.

Description of the Related Art

A plurality of micro light emitting diodes (LEDs) are grown andmanufactured in a chip form on a wafer (growth substrate) through anepitaxial process, and the like. The micro LEDs manufactured asdescribed above may be generally transferred onto a relay substrate andthen transferred onto a target substrate to configure a display module.

A laser transfer manner may be used to transfer the micro LEDs on therelay substrate to the target substrate by radiating a laser beam onto arear surface of the relay substrate (a plurality of micro LEDs arearranged on a front surface of the relay substrate) may be used.

However, in a case of transferring the micro LEDs in the laser transfermanner, there is a problem that accuracy of the laser beam isnon-uniform. Therefore, when the laser beam is irradiated to a micro LEDat a predetermined position on the relay substrate at the time oftransferring the micro LEDs, the laser beam also affects micro LEDs inthe vicinity of the micro LED at the predetermined position. That is,portions of the micro LEDs in the vicinity of the micro LED at thepredetermined position, which are adjacent to the micro LED to betransferred, are separated from the relay substrate, such that the microLEDs may take a posture inclined with respect to the relay substrate.The micro LEDs taking the inclined posture as described above may not beaccurately transferred to designated positions on the target substrateresulting in a significant decrease in transfer efficiency.

To solve such a problem, an optical system such as a homogenizer hasbeen arranged on an irradiation path of the laser beam. However, evenwith such a measure, it was difficult to improve accuracy of a point atwhich the laser beam is focused on the relay substrate.

Therefore, a size of the laser beam (a size of the point at which thelaser beam is focused on the relay substrate) has increased as comparedwith a size of the micro LED, and the micro LEDs have been arranged atwide intervals so that the micro LEDs in the vicinity of the micro LEDto be transferred other than the micro LED to be transferred are notaffected by the laser beam. For this reason, it was difficult tomaximize the number of micro LEDs that may be arranged as compared withan area of the relay substrate.

Due to such a problem, the number of times of replacement of the relaysubstrate in a transfer process has increased, and a working timerequired for the transfer process has increased, resulting in anincrease in a manufacturing cost.

SUMMARY

Embodiments of the disclosure overcome the above disadvantages and otherdisadvantages not described above. Also, the disclosure is not requiredto overcome the disadvantages described above, and an embodiment of thedisclosure may not overcome any of the problems described above.

Provided are a display module and a method of manufacturing the displaymodule using a transfer substrate capable of maximizing the number ofmicro LEDs that may be arranged on the transfer substrate by forming ascreen layer for compensating for accuracy of a laser beam on a rearsurface of the transfer substrate to minimize an interval between microLEDs, and a display module manufactured by the same.

In accordance with an aspect of the disclosure there is provided adisplay module including: a substrate; a thin film transistor (TFT)layer formed on one surface of the substrate; and a plurality of microlight emitting diodes (LEDs) disposed on the TFT layer. The plurality ofmicro LEDs are transferred from a transfer substrate to the TFT layer bya laser beam radiated to the transfer substrate through openings of amask. The openings correspond to regions in which the respective microLEDs of the transfer substrate are arranged and the openings correspondto a width, a length, or a unit area of each of the micro LEDs.

The mask may be disposed on a first surface of the transfer substrateopposite to a second surface of the transfer substrate on which theplurality of micro LEDs are arranged prior to being transferred from thetransfer substrate to the TFT layer by the laser beam.

Each opening of the mask may be arranged at a position corresponding toa corresponding micro LED among the plurality of micro LEDs disposed onthe transfer substrate prior to being transferred from the transfersubstrate to the TFT layer by the laser beam.

The mask and the plurality of micro LEDs may be arranged on a surface ofthe transfer substrate, and each micro LED of the transfer substrate isinserted into a corresponding opening of the mask prior to beingtransferred from the transfer substrate to the TFT layer by the laserbeam.

The mask may include a first portion formed on a first surface of thetransfer substrate on which the plurality of micro LEDs are arrangedprior to being transferred from the transfer substrate to the TFT layerby the laser beam and a second portion formed on a second surface of thetransfer substrate.

The mask may include a metal material that reflects or absorbs the laserbeam.

The mask may include chromium (Cr) or an Invar alloy (Ni—Fe-basedalloy).

In accordance with an aspect of the disclosure there is provided amethod of manufacturing a display module by transferring a plurality ofmicro LEDs arranged on a transfer substrate to a target substrate,including: loading the transfer substrate and the target substrate ontofirst and second stages of a transfer apparatus, respectively; movingthe target substrate and the transfer substrate to transfer positions;and radiating a concentrated laser beam to regions in which therespective micro LEDs of the transfer substrate are arranged throughopenings of a mask, each of the openings corresponding to a width, alength, or a unit area of each of the micro LEDs arranged on thetransfer substrate.

The openings of the mask may be arranged at positions corresponding tothe micro LEDs of the transfer substrate.

In accordance with an aspect of the disclosure there is provided anon-transitory computer readable recording medium comprising a programfor executing a method of manufacturing a display module by transferringa plurality of micro LEDs arranged on a transfer substrate to a targetsubstrate. The method of manufacturing the display module includes:loading the transfer substrate and the target substrate onto first andsecond stages of a transfer apparatus, respectively; moving the targetsubstrate and the transfer substrate to transfer positions; andradiating a concentrated laser beam to regions in which the respectivemicro LEDs of the transfer substrate are arranged through openings of amask, each of the openings corresponding to a width, a length, or a unitarea of each of the micro LEDs arranged on the transfer substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a block diagram schematically illustrating a micro lightemitting diode (LED) transfer apparatus according to an embodiment;

FIG. 2 is a view illustrating one surface of a transfer substrateaccording to an embodiment;

FIG. 3 is a view illustrating the other surface of the transfersubstrate according to an embodiment;

FIG. 4 is a cross-sectional view taken along line A-A of FIG. 3;

FIG. 5 is a view illustrating an example of compensating for accuracy ofa laser beam by a mask when sizes or focusing positions of the laserbeam are different from each other;

FIG. 6 is a view illustrating an example of compensating for accuracy ofa laser beam by a mask when sizes or focusing positions of the laserbeam are different from each other;

FIG. 7 is a view illustrating an example of compensating for accuracy ofa laser beam by a mask when sizes or focusing positions of the laserbeam are different from each other;

FIG. 8 is a view illustrating a part of a display module to which aplurality of micro LEDs are transferred using a transfer substrateaccording to an embodiment;

FIG. 9 is a flowchart illustrating a method of manufacturing a displaymodule according to an embodiment;

FIG. 10 is a cross-sectional view illustrating a transfer substrateaccording to another embodiment;

FIG. 11 is a view illustrating an example of performing a transferprocess using a transfer substrate according to another embodiment; and

FIG. 12 is a cross-sectional view illustrating a transfer substrateaccording to still another embodiment.

DETAILED DESCRIPTION

Embodiments will be described with reference to the accompanyingdrawings. However, the disclosure is not limited to the embodimentsdescribed below, but may be implemented in several forms and may bevariously modified. A description for these embodiments is provided onlyto make the disclosure complete and allow those skilled in the art towhich the disclosure pertains to completely recognize the scope of theembodiments. In the accompanying drawings, sizes of components may beenlarged as compared with actual sizes for convenience of explanation,and ratios of the respective components may be exaggerated or reduced.

It will be understood that when an element is referred to as being“connected,” or “coupled,” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected,” or “directly coupled,” to another element, there are nointervening elements present. Other expressions describing arelationship between components, for example, “between” and “directlybetween” may be similarly interpreted.

Terms such as ‘first’ and ‘second’ may be used to describe variouscomponents, but the components are not to be interpreted to be limitedto these terms. These terms may be used only to distinguish onecomponent from other components. For example, a first component may benamed a second component and the second component may also be similarlynamed the first component, without departing from the scope of thedisclosure.

Singular forms are intended to include plural forms unless the contextclearly indicates otherwise. It may be interpreted that terms “include”,“have”, or the like, specify the presence of features, numerals, steps,operations, components, parts, and combinations thereof mentioned in thespecification, or a combination thereof, but do not preclude theaddition of one or more other features, numerals, steps, operations,components, parts, or combinations thereof.

The expression, “at least one of a, b, and c,” should be understood asincluding only a, only b, only c, both a and b, both a and c, both b andc, or all of a, b, and c.

Terms used to describe embodiments may be interpreted as meanings thatare generally known to those skilled in the art unless definedotherwise.

A display module manufactured according to embodiments may include asubstrate having a thin film transistor (TFT) layer formed on onesurface thereof, a plurality of micro light emitting diodes (LEDs)arranged in a state of being electrically connected to the TFT layer,and wirings electrically connecting circuits arranged on a rear surfaceof the substrate to each other. The TFT layer may be formed integrallywith one surface of the substrate through an epitaxial process or may bemanufactured in a film form through a separate process and be thenattached to one surface of the substrate. The TFT layer may include aTFT circuit and a plurality of terminals to which the micro LEDs areelectrically connected. In addition, a plurality of connection pads towhich one ends of side wirings that may be formed at edge portions ofthe substrate are electrically connected, data signal wirings, gatesignal wirings, and power supply wirings may be patterned on the TFTlayer. Here, the substrate may correspond to a target substrate to bedescribed later, may be any one of a glass substrate, a flexiblesubstrate, or a plastic substrate, and may be referred to as abackplane.

The display module according to embodiments may include a rear substrateelectrically connected to a rear surface of the substrate through aflexible printed circuit (FPC). Here, the rear substrate may be formedin a thin film shape or a thin glass shape having a thickness of severaltens of μm (for example, 50 μm or less). When the rear substrate isformed in the thin film shape, the rear substrate may be formed of aplastic material, for example, any one of polyimide (PI), polyethyleneterephthalate (PET), polythersulfone (PES), polyethylene naphtalate(PEN), or polycarbonate (PC).

The substrate according to an embodiment may include side wirings formedon edge portions thereof. The side wirings may electrically connectfirst connection pads formed on edge portions of a front surface of thesubstrate and second connection pads formed on a rear surface of thesubstrate to each other. To this end, the side wiring may be formedalong the front surface, side end surfaces, and the rear surface of thesubstrate, and may have one end electrically connected to the firstconnection pad and the other end electrically connected to the secondconnection pad. In this case, the side wiring is partially formed on theside end surface of the substrate, and may thus protrude from a side endsurface of a TFT substrate by a thickness of the side wiring. In thiscase, the rear substrate may be electrically connected to the secondconnection pad through the FPC. A driver integrated circuit (IC) mountedon the rear surface of the TFT substrate may be directly connected tothe second connection pad or be indirectly connected to the secondconnection pad through a separate wiring.

A plurality of display modules configured as described above may bearranged in a tiled type to manufacture a large display apparatus.

A display module according to the disclosure may be a micro lightemitting diode (micro LED or μLED) display panel. The micro LED displaypanel is one of the flat panel display panels, and includes a pluralityof inorganic LEDs each having a size of 100 micrometers or less. Themicro LED display panel provides a contrast, a response time, and energyefficiency more excellent than those of a liquid crystal display (LCD)panel requiring a backlight unit. Both of the organic LED (OLED) and themicro LED, which is an inorganic light emitting element, have goodenergy efficiency, but the micro LED has a higher brightness andluminous efficiency and a longer lifespan than those of the OLED. Themicro LED may be a semiconductor chip capable of emitting light byoneself when power is supplied thereto. The micro LED has a fastreaction speed, low power, and high luminance. Specifically, the microLED has a higher efficiency of converting electricity to photons thanthat of an existing liquid crystal display (LCD) or organic lightemitting diode (OLED). That is, the micro LED has a higher “brightnessper watt” than that of an existing LCD or OLED display. Therefore, themicro LED may achieve the same brightness as that of the existing LED(whose width, length, and height exceed 100 μm) or OLED with about ahalf of energy of the existing LED or OLED.

In addition, the micro LED may implement a high resolution and anexcellent color, contrast, and brightness, and may thus accuratelyexpress a wide range of colors and implement a clear screen even in theoutdoors in which sunlight is bright. In addition, the micro LED isresistant to a burn-in phenomenon and generates a small amount of heat,such that a long lifespan of the micro LED is ensured withoutdeformation of the micro LED.

The micro LED according to the disclosure may have a flip chip structurein which anode and cathode electrodes of the micro LED are formed on afirst surface and a light emitting surface is formed on a second surfaceopposite to the first surface on which the anode and cathode electrodesare formed.

In addition, a transfer substrate mentioned in the disclosure is a relaysubstrate in a state where a plurality of micro LEDs are transferredfrom a growth substrate in which the plurality of micro LEDs are grownor is sufficient as long as it is a substrate in a state where the microLEDs may be transferred to a target substrate. Hereinafter, in thedisclosure, the transfer substrate and the relay substrate may be usedinterchangeably.

In the disclosure, the transfer substrate may be a multi-color substrateincluding at least two of red, green, blue, and white micro LEDs, or amono-color substrate including only single-color micro LEDs of the red,green, blue, and white micro LEDs.

In the disclosure, when the micro LEDs are laser-transferred from thetransfer substrate to the target substrate, a laser beam may beconcentrated on a desired point through a mask arranged between thetransfer substrate and a laser oscillator. In this case, each ofopenings of the mask may be formed to correspond to a width, a length ora unit area of each of the micro LEDs. Therefore, the laser beamradiated toward the transfer substrate is accurately radiated only toregions in which respective micro LEDs of the transfer substrate arearranged through the openings of the mask, and the micro LEDs may thusbe arranged on the transfer substrate so that an interval (or a pitch)therebetween is closer than that in the related art.

In the disclosure, the transfer of the micro LEDs may refer to not onlylaser-transferring the micro LEDs from the transfer substrate to thetarget substrate, but also laser-transferring the micro LEDs from thegrowth substrate to the transfer substrate. In both of the casesdescribed above, the laser-transfer may be performed using the mask.Here, the growth substrate may be a wafer for epitaxially growing themicro LEDs.

The display module according to the disclosure may be installed in andapplied to a wearable device, a portable device, a handheld device, andan electronic product or an electrical component requiring variousdisplays, in a single unit, or may be applied to a display device suchas a monitor for a PC, a high resolution TV, a signage, and anelectronic display through a plurality of assembly arrangements in amatrix type.

Hereinafter, a structure of a micro LED transfer apparatus according tothe disclosure will be described with reference to FIG. 1.

FIG. 1 is a block diagram schematically illustrating a micro LEDtransfer apparatus according to an embodiment.

Referring to FIG. 1, a micro LED transfer apparatus 1 according to anembodiment may include a transfer assembly 10 for transferring aplurality of micro LEDs arranged in a predetermined arrangement on atransfer substrate 50 (see FIG. 2) to a target substrate 70 (see FIG.5), first and second stages 21 and 22 arranged adjacent to the transferassembly 10 and each moving the target substrate and the transfersubstrate in X, Y, and Z axis directions, a memory 30 in whichcharacteristic information of each of the plurality of micro LEDs isstored, and a processor 40 controlling the transfer assembly 10 and thefirst and second stages 21 and 22 to determine positions where theplurality of micro LEDs are to be arranged, respectively, on thetransfer substrate 50 on the basis of the stored characteristicinformation and transfer the plurality of micro LEDs to the determinedpositions.

The transfer assembly 10 may simultaneously transfer predetermined microLEDs from a transfer substrate in which the plurality of micro LEDs arearranged to the target substrate in a laser lift-off (LLO) manner.

The transfer assembly 10 may include a laser oscillator for radiating alaser beam toward the transfer substrate 50 to perform a transferprocess in the LLO manner. The transfer assembly 10 may further includeimaging components for identifying a current location of the transfersubstrate and target substrate.

The first stage 21 may include a clamp and one or more motors. The firststage 21 may be configured to detachably clamp the transfer substrate 50on an upper surface of the first stage 21, and may linearly move alongthe X axis, the Y axis, and the Z axis and rotate around the Z axis in astate where it clamps the transfer substrate 50. For example, the clampmay be used to detachably clamp the transfer substrate 50, and the oneor more motors may control the linear movement along the X axis, the Yaxis and the Z axis, and rotation around the Z axis.

The second stage 22 may include a clamp and one or more motors. Thesecond stage 22 may be configured to detachably clamp the targetsubstrate 70 on an upper surface of the second stage 22, and maylinearly move along the X axis, the Y axis, and the Z axis and rotatearound the Z axis in a state where it clamps the target substrate 70.For example, the clamp may be used to detachably clamp the transfersubstrate 50, and the one or more motors may control the linear movementalong the X axis, the Y axis and the Z axis, and rotation around the Zaxis.

In addition, the micro LED transfer apparatus 1 may include the memory30 and the processor 40.

The memory 30 may be implemented as at least one of a flash memory type,a read only memory (ROM), a random access memory (RAM), a hard disktype, a multimedia card micro type, or a card type memory (for example,a secure digital (SD) or XD memory).

In addition, the memory 30 may be electrically connected to theprocessor 40 to transmit a signal and information to the processor 40.Therefore, the memory 30 may store characteristic information of aplurality of micro LEDs that are input or radiated and transmit thestored characteristic information to the processor 40.

The processor 40 controls a general operation of the micro LED transferapparatus 1. That is, the processor 40 may be electrically connected tothe transfer assembly 10 and the first and second stages 21 and 22 tocontrol each component.

For example, the processor 40 may control the transfer assembly 10 andthe first and second stages 21 and 22 to transfer a plurality of microLEDs from growth substrates to a temporary substrate and transfer theplurality of micro LEDs from the temporary substrate to the transfersubstrate 50.

In addition, the processor 40 may control the transfer assembly 10 andthe first and second stages 21 and 22 to transfer the plurality of microLEDs arranged on the transfer substrate 50 to the target substrate 70.The disclosure is not limited to controlling all components by a singleprocessor 40, and respective components of the micro LED transferapparatus 1 may be controlled using a plurality of independentprocessors, respectively.

Here, the processor 40 may include one or more of a central processingunit (CPU), a controller, an application processor (AP), a communicationprocessor (CP), or an ARM processor.

In addition, the processor 40 may be electrically connected to thememory 30 to use the characteristic information of the plurality ofmicro LEDs stored in the memory 30. The characteristic information ofthe plurality of micro LEDs may be data for securing uniformity in anentire arrangement of the plurality of micro LEDs at the time oftransferring the plurality of micro LEDs from the growth substrates tothe temporary substrate.

Specifically, a process of transferring the plurality of micro LEDs fromeach growth substrate to the transfer substrate 50 through the temporarysubstrate using the characteristic information of the plurality of microLEDs may be as follows.

The processor 40 inspects characteristics of a plurality of micro LEDseach formed on red, green, and blue growth substrates, and analyzesluminance, wavelengths, and the like of the micro LEDs for each regionof each growth substrate. An analysis result may be stored in the memory30. The processor 40 controls some imaging device to capture images ofthe micro LEDs which are then analyzed.

When the characteristic inspection is completed, the processor 40simulates a combination of each position for optimal arrangement of aplurality of red, green, and blue micro LEDs in consideration ofuniformity at the time of arranging the plurality of red, green, andblue micro LEDs from each growth substrate onto the temporary substrate,and the like, on the basis of the analysis result.

When the optimal arrangement of the plurality of red, green, and bluemicro LEDs to be arranged on the temporary substrate is set through thesimulation, the processor 40 may form a data map on the basis of theoptimal arrangement. A data map may be stored in the memory 30.

Subsequently, the micro LEDs of each growth substrate are sequentiallytransferred to a single temporary substrate for each color in the LLOmanner on the basis of the data map. Alternatively, the micro LEDs ofeach growth substrate may be transferred to corresponding respectivetemporary substrates.

The plurality of micro LEDs transferred to the temporary substrate asdescribed above may be transferred to the transfer substrate 50 in theLLO manner.

Hereinafter, a structure of the transfer substrate 50 according to anembodiment will be described with reference to FIGS. 2 to 4.

FIG. 2 is a view illustrating one surface (or a front surface) of atransfer substrate according to an embodiment, FIG. 3 is a viewillustrating the other surface (or a rear surface) of the transfersubstrate according to an embodiment, and FIG. 4 is a cross-sectionalview taken along line A-A of FIG. 3.

Referring to FIGS. 2 to 4, the transfer substrate 50 may include a glasssubstrate 51, an adhesive layer 53 formed on a front surface of theglass substrate 51, and a mask 55 formed on a rear surface of the glasssubstrate 51 and having a constant pattern, and a plurality of microLEDs 60 arranged on the adhesive layer 53.

The glass substrate 51 may be a transparent substrate formed ofsapphire, silicon, or transparent glass to be used in a process to whichthe LLO manner is applied.

The adhesive layer 53 may be referred to as a dynamic release layer(DRL), and may be formed of a polyimide (PI) material to be easilyseparated at the time of transferring the micro LEDs to the targetsubstrate 70 in the LLO manner.

The mask 55 may not block a portion of the laser beam transferred to thetransfer substrate 50 during the transfer process, and may block theother portion of the laser beam. To selectively block the laser beam asdescribed above, the mask 55 may have a pattern in which an arrangementof the plurality of micro LEDs 60 is considered.

For example, when the plurality of micro LEDs 60 arranged on the frontsurface of the transfer substrate 50 are arranged in a lattice form atconstant pitches P1 and P2 as illustrated in FIG. 2, the mask 55 formedon the rear surface of the transfer substrate 50 may be formed in apattern of a lattice form as illustrated in FIG. 3. The mask 55 may becoated at a predetermined thickness on the transfer substrate 50 bysputtering in a vacuum chamber.

In this case, the pattern of the mask 55 may have openings 57 formed inregions corresponding to the micro LEDs, respectively. In this case, asize (horizontal and vertical lengths) of the opening 57 may correspondto a size (horizontal and vertical lengths) of the micro LED. Inaddition, intervals D1 and D2 between the openings 57 may be the same asthose between the micro LEDs.

As described above, in the mask 55, the openings 57 having the same sizeas that of the micro LED are formed in regions to which the laser beamis to be radiated, such that accuracy of the laser beam may becompensated for so that the laser beam may be accurately radiated onlyto the corresponding micro LED even though a size of the laser beam isslightly larger than that of the micro LED.

In addition, the transfer substrate 50 according to an embodiment mayinclude the mask 55 in which the openings 57 corresponding to therespective micro LEDs 60 are formed, such that an interval G between themicro LEDs arranged on the front surface of the transfer substrate 50may be narrowed as much as possible. Therefore, in the transfersubstrate 50 according to an embodiment, a larger number of micro LEDsmay be arranged on the transfer substrate 50 than that in the relatedart.

The mask 55 may be formed before the plurality of micro LEDs aretransferred from the temporary substrate to the transfer substrate.However, the disclosure is not limited thereto, and the mask 55 may beformed on the rear surface of the transfer substrate 50 after theplurality of micro LEDs 60 are transferred from the temporary substrateto the front surface of the transfer substrate 50.

The mask 55 is preferably formed of a material that may reflect orabsorb the laser beam to block the laser beam. For example, the mask 55may be formed of a metal material such as chromium (Cr), an Invar alloy(Ni—Fe alloy), or the like.

In addition, a case where the mask 55 is stacked and formed integrallywith the transfer substrate 50 is described in the disclosure, but thedisclosure is not limited thereto, and the mask 55 may be formed as aseparate mask from the transfer substrate 50. In this case, the separatemask may be arranged in a state where it is in close contact with therear surface of the transfer substrate 50 at the time of transferringthe micro LEDs, or may be arranged at a predetermined distance from therear surface of the transfer substrate 50.

Hereinafter, a role of the mask 55 at the time of laser-transferring themicro LEDs from the transfer substrate 50 to the target substrate 70will be described with reference to FIGS. 5 to 7.

FIGS. 5 to 7 are views illustrating an example of compensating foraccuracy of a laser beam by a mask when sizes or focusing positions ofthe laser beam are different from each other.

To transfer the plurality of micro LEDs from the transfer substrate 50to the target substrate 70 through the laser-transfer, the transfersubstrate 50 and the target substrate 70 may be set to any positionswhere the laser beam is radiated by the first and second stages 21 and22 for each moving the transfer substrate 50 and the target substrate70.

To transfer the micro LEDs in this state, as illustrated in FIG. 5, alaser beam L1 is radiated toward a predetermined point on the transfersubstrate 50. In this case, a size of the radiated laser beam L1 may belarger than that of the opening 57. An edge region of the laser beam L1is blocked by portions 55 a and 55 b surrounding the correspondingopening 57.

The laser beam L1 may be radiated to the transfer substrate 50 by a sizecorresponding to the opening 57. Therefore, the laser beam L1 may beblocked through the mask 55 so that micro LEDs in the vicinity of amicro LED to be transferred other than the micro LED to be transferredare not affected by the laser beam L1.

Referring to FIG. 6, even in a case where a laser beam L2 having a sizelarger than that of the laser beam L1 illustrated in FIG. 5 is radiatedto the transfer substrate 50, an edge region of the laser beam L2 may beblocked by portions 55 a and 55 b surrounding the corresponding opening57, and accuracy of the laser beam L2 may thus be compensated for.

Referring to FIG. 7, even in a case where a laser beam L3 having thesame size as that of laser beam L1 illustrated in FIG. 5 is eccentric tosome extent in relation to the corresponding opening 57, micro LEDs inthe vicinity of a micro LED to be transferred other than the micro LEDto be transferred may not be affected by the laser beam L3 by portions55 a and 55 b surrounding the opening of the mask 55.

The transfer substrate 50 according to an embodiment may compensate forthe accuracy of the laser beam through the mask 55 in the transferprocess as described above.

Meanwhile, the laser transfer process according to the disclosuredescribed above may be implemented in a form of an application that maybe installed on the micro LED transfer apparatus 1 or may be implementedonly by software upgrade or hardware upgrade for the micro LED transferapparatus 1.

In addition, diverse embodiments described above may be performedthrough an embedded server provided in the micro LED transfer apparatus1 or an external server of the micro LED transfer apparatus 1.

The diverse embodiments described above may be implemented in a computeror a non-transitory computer readable recording medium using software,hardware, or a combination of software and hardware. In some cases,embodiments described in the disclosure may be implemented by theprocessor 40 itself. According to a software implementation, embodimentssuch as procedures and functions described in the specification may beimplemented by separate software modules. Each of the software modulesmay perform one or more functions and operations described in thedisclosure.

Computer instructions for performing a processing operation of the microLED transfer apparatus 1 according to the diverse embodiment describedabove may be stored in a non-transitory computer-readable medium. Thecomputer instructions stored in the non-transitory computer-readablemedium cause a specific device to perform the processing operations ofthe micro LED transfer apparatus 1 according to the diverse embodimentsdescribed above when they are executed by a processor of the specificdevice.

The non-transitory computer-readable medium is not a medium that storesdata for a while, such as a register, a cache, a memory, or the like,but means a medium that semi-permanently stores data and is readable bythe device. A specific example of the non-transitory computer-readablemedium may include a compact disk (CD), a digital versatile disk (DVD),a hard disk, a Blu-ray disk, a universal serial bus (USB), a memorycard, a read only memory (ROM), or the like.

FIG. 8 is a view illustrating an arrangement of the plurality of microLEDs transferred from the transfer substrate 50 to the target substrate70.

Referring to FIG. 8, red, green, and blue micro LEDs may form a singlegroup on the target substrate 70, and a plurality of single groups maybe arranged to maintain a predetermined pitch therebetween. In thiscase, the single group may further include a white micro LED.

In addition, the single groups transferred to the target substrate 70 donot need to be limited to a form in which they are arranged in a line asillustrated in FIG. 8, and may be arranged in various forms.

In the disclosure, the target substrate 70 may include a thin filmtransistor (TFT) layer formed on a front surface thereof on which theplurality of micro LEDs 60 are transferred. Cathode electrodes 61 (seeFIG. 5) and anode electrodes 62 (see FIG. 5) of the plurality of microLEDs 60 transferred to the target substrate 70 may be electricallyconnected to respective driving circuits provided in the TFT layer atthe time of transferring the plurality of micro LEDs 60. In addition,the target substrate 70 may include a wiring electrically connecting theTFT layer and a circuit arranged on a rear surface of the targetsubstrate 70 to each other. In this case, the wiring may be formed on aside surface (or an edge region) of the target substrate 70.

The target substrate 70 including each of the components as describedabove may be a display module. A plurality of display modules may beconnected to each other in various forms such as a straight line form ora lattice form to implement a large display apparatus.

Hereinafter, processes of manufacturing a display module using atransfer substrate according to an embodiment will be sequentiallydescribed with reference to FIG. 9.

FIG. 9 is a flowchart illustrating a method of manufacturing a displaymodule according to an embodiment.

First, the transfer substrate 50 is loaded onto the first stage 21, andthe target substrate 70 is loaded onto the second stage 22 (S11).

Then, the target substrate 70 and the transfer substrate 50 are moved topredetermined transfer positions by driving the first and second stages21 and 22 (S12).

Then, the micro LEDs 60 of the transfer substrate 50 are transferred tothe target substrate 70 by concentrating and radiating a laser beam onand to regions in which the micro LEDs 60 are arranged on the transfersubstrate 50 through the openings 57 of the mask 55 provided on thetransfer substrate 50 (S13). In this case, each of the openings 57 ofthe mask 55 may have a size corresponding to a width, a length or a unitarea of each of the micro LEDs arranged on the transfer substrate 50.

FIG. 10 is a cross-sectional view illustrating a transfer substrateaccording to another embodiment, and FIG. 11 is a view illustrating anexample of performing a transfer process using a transfer substrateaccording to another embodiment.

A case where the mask 55 is formed on the rear surface of the transfersubstrate 50 on which the micro LEDs 60 are not present has beendescribed, but the disclosure is not limited thereto, and the mask mayalso be formed on the front surface of the transfer substrate on whichthe micro LEDs are arranged.

Referring to FIG. 10, a transfer substrate 150 according to anotherembodiment may include a transparent substrate 151 and an adhesive layer153 which is formed on a front surface of the transparent substrate 151and to which a plurality of micro LEDs are temporarily attached, similarto the transfer substrate 50 described above.

The transfer substrate 150 according to another embodiment may include amask 155 formed on the adhesive layer 153. In this case, the mask 155may be applied to the remaining region except for a region occupied bythe plurality of micro LEDs 160 on the adhesive layer 153.

The mask 155 may be formed in a pattern of a lattice form, similar tothe mask 55 of the transfer substrate 50 described above. In this case,the mask 155 is formed between the respective micro LEDs 160 and outsidethe outermost micro LEDs, and is not formed in a region occupied by therespective micro LEDs 160.

Referring to FIG. 11, a laser beam L4 is radiated to a predeterminedpoint of the transfer substrate 150 to transfer a predetermined microLED 160 from the transfer substrate 150 to a target substrate 170.

In this case, even though a size of the laser beam L4 is larger thanthat of the corresponding micro LED 160, the laser beam L4 is reflectedor absorbed by portions 155 a and 155 b surrounding the correspondingmicro LED 160, such that micro LEDs arranged in the vicinity of thecorresponding micro LED 160 are not affected by the laser beam L4.

FIG. 12 is a cross-sectional view illustrating a transfer substrateaccording to still another embodiment.

Referring to FIG. 12, a transfer substrate 250 according to stillanother embodiment may include a mask consisting of a first portion 255formed on a rear surface thereof and a second portion 256 formed on afront surface thereof.

The first portion 255 and the second portion 256 may be formed inpatterns of lattice forms corresponding to each other. In this case, thesecond portion 256 is formed between the respective micro LEDs 260 andoutside the outermost micro LEDs, and is not formed in a region occupiedby the respective micro LEDs 260.

Each opening 257 of the first portion 255 may be formed to have a sizelarger than that of the micro LED 260. Therefore, a width D3 of thefirst portion 255 may be smaller than a width D4 of the second portion256.

The width D3 of the first portion 255 or the size of the opening 257 ofthe first portion 255 may be set in consideration of a focusing angle ofa laser beam L5 radiated to the transfer substrate 250. In this case,inner surfaces 255 c and 255 d of the opening 257 are preferably formedto be inclined to have a predetermined angle. However, the disclosure isnot limited thereto, and the inner surfaces 255 c and 255 d of theopening 257 may also be formed without being inclined.

Meanwhile, the width D3 of the first portion 255 is not necessarilysmaller than the width D4 of the second portion 256, and may be the sameas the width D4 of the second portion 256. Therefore, the width D3 ofthe first portion 255 may be in a range in which it is equal to orsmaller than the width D4 of the second portion 256.

In FIG. 12, reference numeral 251 denotes a transparent substrate,reference numeral 253 denotes an adhesive layer, and reference numeral270 denotes a target substrate.

Although the diverse embodiments have been individually describedhereinabove, the respective embodiments are not necessarily implementedsingly, and may also be implemented so that configurations andoperations thereof are combined with those of one or more otherembodiments.

Although embodiments have been illustrated and described hereinabove,the disclosure is not limited to the specific embodiments describedabove, but may be variously modified by those skilled in the art towhich the disclosure pertains without departing from the scope andspirit of the disclosure claimed in the claims. These modificationsshould also be understood to fall within the scope of the disclosure.

What is claimed is:
 1. A display module comprising: a substrate; a thinfilm transistor (TFT) layer formed on one surface of the substrate; anda plurality of micro light emitting diodes (LEDs) disposed on the TFTlayer, wherein the plurality of micro LEDs are transferred from atransfer substrate to the TFT layer by a laser beam radiated to thetransfer substrate through openings of a mask, wherein the openingscorrespond to regions in which the respective micro LEDs of the transfersubstrate are arranged and the openings correspond to a width, a length,or a unit area of each of the micro LEDs.
 2. The display module asclaimed in claim 1, wherein the mask is disposed on a first surface ofthe transfer substrate opposite to a second surface of the transfersubstrate on which the plurality of micro LEDs are arranged prior tobeing transferred from the transfer substrate to the TFT layer by thelaser beam.
 3. The display module as claimed in claim 2, wherein eachopening of the mask is arranged at a position corresponding to acorresponding micro LED among the plurality of micro LEDs disposed onthe transfer substrate prior to being transferred from the transfersubstrate to the TFT layer by the laser beam.
 4. The display module asclaimed in claim 1, wherein the mask and the plurality of micro LEDs arearranged on a surface of the transfer substrate, and wherein each microLED of the transfer substrate is inserted into a corresponding openingof the mask prior to being transferred from the transfer substrate tothe TFT layer by the laser beam.
 5. The display module as claimed inclaim 1, wherein the mask includes a first portion formed on a firstsurface of the transfer substrate on which the plurality of micro LEDsare arranged prior to being transferred from the transfer substrate tothe TFT layer by the laser beam and a second portion formed on a secondsurface of the transfer substrate.
 6. The display module as claimed inclaim 1, wherein the mask comprises a metal material that reflects orabsorbs the laser beam.
 7. The display module as claimed in claim 6,wherein the mask comprises chromium (Cr) or an Invar alloy (Ni—Fe-basedalloy).
 8. A method of manufacturing a display module by transferring aplurality of micro LEDs arranged on a transfer substrate to a targetsubstrate, comprising: loading the transfer substrate and the targetsubstrate onto first and second stages of a transfer apparatus,respectively; moving the target substrate and the transfer substrate totransfer positions; and radiating a concentrated laser beam to regionsin which the respective micro LEDs of the transfer substrate arearranged through openings of a mask, each of the openings correspondingto a width, a length, or a unit area of each of the micro LEDs arrangedon the transfer substrate.
 9. The method of manufacturing a displaymodule as claimed in claim 8, wherein the openings of the mask arearranged at positions corresponding to the micro LEDs of the transfersubstrate.
 10. A non-transitory computer readable recording mediumcomprising a program for executing a method of manufacturing a displaymodule by transferring a plurality of micro LEDs arranged on a transfersubstrate to a target substrate, wherein the method of manufacturing thedisplay module includes: loading the transfer substrate and the targetsubstrate onto first and second stages of a transfer apparatus,respectively; moving the target substrate and the transfer substrate totransfer positions; and radiating a concentrated laser beam to regionsin which the respective micro LEDs of the transfer substrate arearranged through openings of a mask, each of the openings correspondingto a width, a length, or a unit area of each of the micro LEDs arrangedon the transfer substrate.